From: Ed Stander (glassact@compuserve.com)
Date: 11/12/01-06:43:51 AM Z
Judy:
True enough - using a metal halide light source is equivalent to using a
stick of dynamite to open a door. However, before one opens the door, one
has to consider the global picture.
There are a lot of processes out there, and each sensitizer appears to
be sensitive to different parts of the spectrum. Further, each binding
agent seems to absorb different parts of the spectrum.
If we knew the ins and outs of each process, we could design a light
source that would direct those watts precisely to the task at hand.
Unfortunately, we don't have any such understanding, as may be shown by
even a cursory reading of the list's archives.
Fluorescent lights (at least those commercially available) give all of
their light in a very narrow wedge of the spectrum. If this happens to be
the right part of the spectrum, all's well and good. Your observations on
cyanotype are right on here.... why use 5000 watts, when you can get away
with 400?
On the other hand, what good are those 400 watts, if they fall outside
of the active zone of the sensitizer? The beauty of the hallies is their
broad spectrum in the UV.
I found this out firsthand when I replaced a narrow spectrum halide
lamp with a wide spectrum one. Times immediately decreased by 500%. The
reason: more light where it counted.
Finally, as to cost... 5000 watts for 30 seconds is how much?
Electricity costs around 12 cents per kilowatt hour. If I used my
light for one hour it would cost me 60 cents. That's 1 cent per kilowatt
minute, or 1/2 a cent per exposure. I can deal with that.
All the best, Judy - and one of these days I'll get that 24 dollars off
to you (even though that comes to nearly 40 hours of exposure time.... )
Cheers, Ed.
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